US5228344A - Method of measuring pressures using a tuning fork crystal oscillator - Google Patents

Method of measuring pressures using a tuning fork crystal oscillator Download PDF

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Publication number
US5228344A
US5228344A US07/743,227 US74322791A US5228344A US 5228344 A US5228344 A US 5228344A US 74322791 A US74322791 A US 74322791A US 5228344 A US5228344 A US 5228344A
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United States
Prior art keywords
tuning fork
fork oscillator
pressure
resonance resistance
resistance
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Expired - Lifetime
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US07/743,227
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English (en)
Inventor
Hisao Hojoh
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Vacuum Products Corp
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Vacuum Products Corp
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Assigned to VACUUM PRODUCTS KABUSHIKI KAISHA reassignment VACUUM PRODUCTS KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: HOJOH, HISAO
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/08—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of piezoelectric devices, i.e. electric circuits therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/0001—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means
    • G01L9/0008—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means using vibrations
    • G01L9/0022—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means using vibrations of a piezoelectric element

Definitions

  • the present invention relates to a method of measuring pressures using a tuning fork crystal oscillator.
  • the fork oscillator In the conventional method that uses the fork oscillator to measure pressures, as described above, the fork oscillator usually has a temperature that is indefinitely varying during the measuring process, which may cause large errors when measuring the pressures in the lower pressure range. This would inadvantageously make accurate pressure measurement impossible.
  • the natural resonance resistance Z 0 as described above remains stable in a wide temperature range (-20° C. to +60° C.), such that it only changes by a factor of several K ohms ( ⁇ ) in that temperature range, while the value of the resistance difference ⁇ Z is decreasing by the order of several K ohms in the pressure range between 10 -1 and 10 -2 Torr, and is decreasing by the order of several tens of ohms in the pressure range between 10 -2 and 10 -3 Torr, which means that the value of ⁇ Z is decreasing as the pressures are reduced.
  • the change in the natural resonance resistance Z 0 that is caused by any changes in the temperature of the fork oscillator cannot be neglected. This therefore imposes limitations on the ability of the fork oscillator to measure the pressures.
  • a pressure measuring probe as shown in FIG. 6, which includes a fork oscillator 41 buried in an aluminum block 42, and a heater 43 and a temperature sensor 44 also buried in the same aluminum block 42 to maintain the fork oscillator 41 at a constant temperature.
  • the aluminum block 42 has an inherent thermal capacity that causes a time lag or delay to occur before the fork oscillator 41 is controlled to reach the specific temperature at which it should be maintained.
  • one problem of the device is the slow response time when the probe is measuring pressures, and another problem is that the measuring circuit must include an additional temperature control circuit for the heater 43 and temperature sensor 44, which makes the measuring circuit more complicated and expensive.
  • the present invention proposes to provide a method whereby a pressure can be measured with high precision using a fork oscillator without the need of providing the extra components of the prior art.
  • a pressure measuring method using a fork oscillator includes determining a pressure in a gaseous substance from a difference ⁇ Z between a natural resonance resistance Z T of the fork oscillator at a determined temperature and its actual resonance resistance Z as measured, wherein the method is characterized by the additional steps of measuring a resonance frequency "f" for the fork oscillator, determining a temperature T of the fork oscillator from the measured frequency "f", and determining the natural resonance resistance Z T at the determined temperature T.
  • the resonance resistance Z may be determined by driving the fork oscillator at a stabilized AC voltage that is applied across it, and then obtaining the resonance current at that time and performing an arithmetic operation.
  • the natural resonance resistance Z T at the temperature T may be measured by setting a voltage equal to a value Z c denoting the natural resonance resistance Z T at a constant temperature (20° C., for example) as reference voltage, obtaining a voltage equal to a difference ⁇ Z T between Z T and Z c at the temperature T from the resonance frequency "f", and enabling an operational amplifier to perform an arithmetic operation on the two input voltages.
  • the output of the operational amplifier determines the natural resonance resistance Z T at the temperature T. In the process described above, the temperature T is determined substantially from the resonance frequency "f", and the temperature T is then used for determining the difference ⁇ Z T .
  • Z T is defined as the natural resonance resistance for the fork oscillator at a temperature T and the value that represents the natural resonance resistance. This value may vary according to changes in temperature.
  • Z c is defined as the natural resonance resistance Z T at a constant temperature (20° C., for example) and the value that represents this resonance resistance. This value may be derived from Z c + ⁇ Z T .
  • ⁇ Z T is defined as the difference between Z T and Z c at a given temperature.
  • the difference ⁇ Z may be determined from the natural resonance resistance Z T of the fork oscillator and the actual resonance resistance Z the measured pressure, even if there are changes in the temperature of the fork oscillator during the measuring process.
  • the pressure may always be measured with high precision without any errors.
  • FIG. 1 is a graphical representation that illustrates characteristics curves showing the relationships between the varying temperature of the fork oscillator used in the embodiments of the present invention and the respective corresponding changes in the resonance frequency and natural resonance resistance;
  • FIG. 2 is a graphical representation that illustrates a characteristics curve showing the pressure difference for the fork oscillator
  • FIG. 3 is a block diagram of a measuring circuit according to one embodiment of the present invention.
  • FIG. 4 is a circuit diagram for an arithmetic circuit in the embodiment of FIG. 3;
  • FIG. 5 is a block diagram of a measuring circuit according to another embodiment of the present invention.
  • FIG. 6 is a front view of a conventional fork oscillator temperature control apparatus.
  • a tuning fork crystal oscillator (which is referred to as a "fork oscillator”) that may be used for purposes of the present invention has linear operational characteristics, as identified by the line “a”, in FIG. 1 showing the relationship between temperature T and the resonance frequency f.
  • the fork oscillator also has curved operational characteristics, as identified by line “b” in FIG. 1, showing the relationship between the temperature T and the natural resonance resistance Z T .
  • a fork oscillator 1 having the operating characteristics described above may be used to constitute a pressure measuring circuit, as shown in FIG. 3.
  • the measuring circuit includes a current/voltage converter 2, a full-wave rectifier 3, a 1/10 attenuator 4, a comparator 5, a voltage-controlled attenuator 6, a full-wave rectifier 7, an arithmetic circuit 8, a frequency counter 9, a digital to analog (D/A) converter 10, and a meter 11.
  • D/A digital to analog
  • the full-wave rectifier 3, 1/10 attenuator 4, comparator 5 and voltage-controlled attenuator 6 form a stabilized AC voltage supply, and the stabilized AC voltage supply and the fork oscillator 1 form a self-excited oscillator.
  • a signal that corresponds to a resonance current in the oscillator circuit is applied through the current/voltage converter 2 and full-wave rectifier 7 to one of the inputs of the arithmetic circuit 8.
  • the signal that corresponds to the resonance current is also the signal that corresponds to the resonance resistance Z
  • the signal that is applied to the one input of the arithmetic circuit 8 effectively represents the signal 1/Z related to the resonance resistance Z.
  • a signal representing ⁇ Z T is applied to the other input of the arithmetic circuit 8 from the frequency counter 9 and D/A converter 10.
  • the arithmetic circuit 8 has an arrangement as shown in FIG. 4, including operational amplifiers OP 1 to OP 3 and a divider 15.
  • the frequency counter 9 and D/A converter 10 respond to the input resonance frequency "f" to operate according to the characteristics curves shown in FIG. 1, and provides the resistance value ⁇ Z T that represents the temperature of the fork oscillator.
  • the operational amplifier OP 1 responds to the input signal ⁇ Z T from the frequency counter and D/A converter and the input reference voltage Z c , and an provides output of -(Z c + ⁇ Z T ). Then, the output of -(Z c + ⁇ Z T ), that is, the negative value of Z T and the value of the resonance resistance Z from the full-wave rectifier 7 are added together, the result of Z-Z T is fed to operational amplifier OP 1 whose output is then fed to OP2, whose output ⁇ Z may be used to drive the meter 11 according to FIG. 2.
  • point A in FIG. A is determined substantially from the resonance frequency "f"
  • point B is determined.
  • the natural resonance resistance Z T of the fork oscillator 1 can be represented any temperature that occurs during the measuring process, rather than using the fixed value Z O in the high vacuum according to the prior art method. Any errors that may be caused by any changes in the temperature of the fork oscillator 1 can be eliminated.
  • FIG. 5 another embodiment of the measuring circuit is shown.
  • This measuring circuit provides a digital display, in contrast to the preceding embodiment that provides an analog display.
  • similar elements are given the same reference numerals as those in the preceding embodiment.
  • This embodiment differs from the preceding embodiment in that the resonance resistance 1/Z from the full-wave rectifier 7 is applied to A/D converter 12 which provides the corresponding digital output.
  • This digital output is applied to CPU 13 together with the output from the frequency counter 9, and CPU 13 performs the arithmetic operations thereon.
  • the output of CPU 13 may be presented in digital form on a display 14.
  • the CPU 13 may perform the same operations as described in the previous embodiment, and may contain a memory for storing programs and the data as shown in FIG. 1.
  • the current embodiment can determine the pressures from the natural resonance resistance Z T at the temperature of the fork oscillator during the measuring process, and can also eliminate any errors that may be caused by any changes in the temperature.
  • the method according to the present invention allows any changes in the temperature of the fork oscillator to be detected, and a pressure difference ⁇ Z to be determined from the natural resonance resistance Z T at that temperature and the measured resonance resistance Z corresponding to the pressure, thereby determining the pressures.
  • a pressure difference ⁇ Z to be determined from the natural resonance resistance Z T at that temperature and the measured resonance resistance Z corresponding to the pressure, thereby determining the pressures.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Fluid Pressure (AREA)
US07/743,227 1990-08-10 1991-08-09 Method of measuring pressures using a tuning fork crystal oscillator Expired - Lifetime US5228344A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2-212417 1990-08-10
JP2212417A JPH0797060B2 (ja) 1990-08-10 1990-08-10 音叉型水晶振動子を用いた圧力の測定方法

Publications (1)

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US5228344A true US5228344A (en) 1993-07-20

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US07/743,227 Expired - Lifetime US5228344A (en) 1990-08-10 1991-08-09 Method of measuring pressures using a tuning fork crystal oscillator

Country Status (5)

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US (1) US5228344A (ko)
EP (1) EP0470853B1 (ko)
JP (1) JPH0797060B2 (ko)
KR (1) KR100189223B1 (ko)
DE (1) DE69128266T2 (ko)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5528939A (en) * 1995-03-21 1996-06-25 Martin; Jacob H. Micromechanical pressure gauge having extended sensor range
US5939635A (en) * 1997-12-02 1999-08-17 Varian Inc. Micromechanical pressure sensor-with improved range
US6629342B1 (en) * 1997-04-14 2003-10-07 Toyo Communication Equipment Co., Ltd. Method for producing an AT-cut resonator
US20120060619A1 (en) * 2010-09-10 2012-03-15 Kulite Semiconductor Products, Inc. Tunable pressure transducer assembly
US11060935B2 (en) 2019-05-01 2021-07-13 Kulite Semiconductor Products, Inc. Pressure transducer assembly with selectable damping inserts
US11852551B2 (en) 2019-05-01 2023-12-26 Kulite Semiconductor Products, Inc. Clog resistant low pass filter for a pressure transducer

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4493139B2 (ja) * 2000-02-02 2010-06-30 キヤノンアネルバ株式会社 電離真空計
JP4592897B2 (ja) * 2000-08-30 2010-12-08 キヤノンアネルバ株式会社 圧力測定装置および複合型圧力測定装置
JP5353358B2 (ja) * 2009-03-26 2013-11-27 富士電機株式会社 真空計
WO2011099238A1 (ja) * 2010-02-12 2011-08-18 株式会社アルバック トランスデューサ型真空計

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4995263A (en) * 1989-01-23 1991-02-26 Balzers Aktiengesellschaft Tuning fork quartz manometer
US4995264A (en) * 1989-01-23 1991-02-26 Balzers Aktiengesellschaft Gas pressure gauge and pressure measuring method
US4995265A (en) * 1989-01-23 1991-02-26 Balzers Aktiengesellschaft Degradation and contamination compensated tuning fork quartz monometer, and method to compensate for tuning quartz degradation and contamination

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60171428A (ja) * 1984-02-16 1985-09-04 Seiko Instr & Electronics Ltd 気体圧力計

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4995263A (en) * 1989-01-23 1991-02-26 Balzers Aktiengesellschaft Tuning fork quartz manometer
US4995264A (en) * 1989-01-23 1991-02-26 Balzers Aktiengesellschaft Gas pressure gauge and pressure measuring method
US4995265A (en) * 1989-01-23 1991-02-26 Balzers Aktiengesellschaft Degradation and contamination compensated tuning fork quartz monometer, and method to compensate for tuning quartz degradation and contamination

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5528939A (en) * 1995-03-21 1996-06-25 Martin; Jacob H. Micromechanical pressure gauge having extended sensor range
US6629342B1 (en) * 1997-04-14 2003-10-07 Toyo Communication Equipment Co., Ltd. Method for producing an AT-cut resonator
US5939635A (en) * 1997-12-02 1999-08-17 Varian Inc. Micromechanical pressure sensor-with improved range
US20120060619A1 (en) * 2010-09-10 2012-03-15 Kulite Semiconductor Products, Inc. Tunable pressure transducer assembly
US8707791B2 (en) * 2010-09-10 2014-04-29 Kulite Semiconductor Products, Inc. Tunable pressure transducer assembly
US10302516B2 (en) * 2010-09-10 2019-05-28 Kulite Semiconductor Products, Inc. Tunable pressure transducer assembly
US11060935B2 (en) 2019-05-01 2021-07-13 Kulite Semiconductor Products, Inc. Pressure transducer assembly with selectable damping inserts
US11698318B2 (en) 2019-05-01 2023-07-11 Kulite Semiconductor Products, Inc. Pressure transducer assembly with selectable damping inserts
US11852551B2 (en) 2019-05-01 2023-12-26 Kulite Semiconductor Products, Inc. Clog resistant low pass filter for a pressure transducer

Also Published As

Publication number Publication date
DE69128266D1 (de) 1998-01-08
EP0470853A3 (en) 1993-01-13
EP0470853A2 (en) 1992-02-12
KR100189223B1 (ko) 1999-06-01
EP0470853B1 (en) 1997-11-26
DE69128266T2 (de) 1998-04-02
JPH0493735A (ja) 1992-03-26
KR920004825A (ko) 1992-03-28
JPH0797060B2 (ja) 1995-10-18

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